The present invention relates to a fluorine-containing material for an optical waveguide which is produced by curing a fluorine-containing prepolymer having a carbon-carbon double bond in its molecular chain, a member obtained from a cured article of the fluorine-containing material for an optical waveguide and an optical waveguide device produced by using the cured article on at least one of a core portion and a clad portion of the device.
Various optical parts have been developed aiming at a high grade optical communication system and economization thereof. Particularly an attention is directed to an optical waveguide as a basic technology for realizing a high density optical interconnection and a waveguide type optical device. Generally optical waveguide materials are required to have characteristics such as easiness in production of a waveguide, controllability of transparency in a region of near infrared wavelength, heat resistance and water resistance.
At present quartz is used most as a material for an optical waveguide. Quartz is high in transparency at a wavelength of from 1,300 to 1,550 nm in a near infrared region and is low in light loss. However there is a problem that a production process is complicated and a waveguide having a large area is difficult to produce. Therefore it is difficult to produce a waveguide type optical device which is excellent in economy and can be used widely for various purposes.
On the other hand, in case of an optical waveguide obtained from a high molecular weight material, since a process for forming a film with a spin coater can be adopted, the waveguide can be produced by an easy process and its area can be made large. However since conventional transparent resin materials such as polystyrene, acrylic resin and polyimide have a large absorption in the above-mentioned near infrared region (poor transparency), a light loss is large and it is difficult to use for the waveguide practically. A trial has been made to reduce light loss by replacing hydrogen in those resins with heavy oxygen (D) or fluorine (F). As a result, though optical characteristics can be improved, it was found that those characteristics were lowered significantly due to water absorption with a lapse of time. Namely, an absorption of light in a near infrared region is increased due to water, thereby increasing a transmission loss.
There has been proposed a non-crystalline fluorine-containing perfluoro polymer having a ring structure as a high molecular weight material which has good transparency in a near infrared region, is relatively low in light loss and has a low water absorption (JP4-190202A, JP2000-81519A, etc.).
Such a non-crystalline fluorine-containing polymer has no problem with transparency, but is low in a glass transition temperature and has a problem with heat resistance. In case of a system where the glass transition temperature was sufficiently increased by changing the structure and proportion of its components, the polymer became fragile and there was a problem that cracking occurred in a process of forming a waveguide. Also in case of the non-crystalline fluorine-containing perfluoro polymer, a range of controllable refractive index is narrow and there is a big restriction in designing of a core-clad type waveguide. For example, when the polymer is used on the core portion of a waveguide, since there is no proper clad material from the viewpoint of refractive index, as mentioned in JP2000-81519A, it is necessary to blend a compound having a high refractive index to the core portion. In case of such a core material, there is a disadvantage that the blended high refractive index component is re-dispersed due to a factor such as an external environmental, which causes non-uniformity of a refractive index inside the core and becomes an influential factor of a transmission loss. As mentioned above, all the problems with the material for a waveguide have not been solved and a novel material for a waveguide which can solve those problems is desired.